A similar shield is described in a 1922 H.G. Fischer & Company
catalog as a "Leaded Glass Shield or Cover for the Radiator Type
Coolidge Tube - either the 10 or 30 M.A." The device shown
here consists of two halves that are attached together with bolts. The
flange through which the bolts penetrate has the following text on it:
"W. & B. Manufacturing Company, New York. Corning. Made
in U.S.A." The glass is completely opaque which would be
advantageous in fluoroscopy where stray light would be undesirable.

The tube would be oriented so that the x-ray beam would leave though the
circular two inch opening in the shield (facing upwards in the above
photo). Note that an enclosed shield like this almost eliminates any
loss of heat through the glass, hence the need for some other heat loss
mechanism (in this case, the radiator fins).